2. Many different types of variable ratio transmissions are known for providing a variable speed ratio between a rotating power source and a rotating load. In a constant speed drive system, it is desired to drive a load such as a generator at constant speed from a variable speed prime mover such as a propulsion engine of an aircraft. The transmission can include a planetary gearset with selectively operable brakes and hydroviscous clutches to provide a constant output speed with variable input speed with minimal slipping of the hydroviscous clutches to minimize the dissipation of energy through the hydroviscous clutches.
Another known constant speed drive has a variable ratio transmission including a planetary gearset and a hydroviscous brake associated therewith to provide a constant speed output from the transmission with varying input speeds.
My copending application Ser. No. 713,879, filed Mar. 18, 1985 now U.S. Pat. No. 4,708,030, granted Nov. 24. 1987, discloses the use of a pair of hydroviscous clutches in association with a planetary gearset for a multi-range starter-generator drive.
A planetary gear transmission having a pair of brakes associated with different gears of the planetary gear transmission providing for either forward or reverse output rotation is shown in De Feo U.S. Pat. No. 3,886,816.
A transmission utilizing a hydroviscous clutch is shown in the Handke U.S. Pat. No. 4,488,626;
A drive train including a viscous clutch is shown in Renneker U.S. Pat. No. 4,562,897.
It is not known in the prior art to have a multi-range dissipative infinitely variable ratio transmission utilizing a planetary gearset having at least four rotatably associated gears with two of the gears defining input and output elements, respectively, and the other two gears being independently rotatable and associated one with each of a pair of hydroviscous brakes with means for selecting which of the brakes is operable and for controlling the slip thereof to provide a ground torque reaction and obtain the desired speed ratio with a minimum of dissipated energy through the slipping hydroviscous brake.